Trick mode using dummy bidirectional predictive pictures

ABSTRACT

The invention concerns a method ( 200 ) or ( 300 ) and system ( 100 ) for performing a trick mode on a video signal containing a plurality of progressively scanned original pictures. The method ( 200 ) includes the steps of: selectively repeating ( 214 ) at least one of the original pictures to convert the video signal to a trick mode video signal in response to a trick mode command; and the step of selectively inserting ( 216 ) at least one dummy bidirectional predictive picture in the trick mode video signal. In addition, the method ( 300 ) can include the step of monitoring ( 316 ) the trick mode video signal so that the dummy bidirectional predictive picture is selectively inserted when the bit rate exceeds a predetermined threshold. Certain pictures in the trick mode video signal can also be modified ( 220 ) ( 328 ) to reflect an intended display order.

BACKGROUND OF THE INVENTION

[0001] 1. Technical Field

[0002] The inventive arrangements relate generally to video systems andmore particularly to video systems that record or replay digitallyencoded video sequences.

[0003] 2. Description of Related Art

[0004] Digital television (DTV) and high-definition television (HDTV)are gaining popularity in today's consumer electronics marketplace. Manypurchasers of these types of television products often buy digital videorecorders or players, such as digital video disc (DVD) recorders orplayers, for purposes of viewing prerecorded programming or recordingtheir favorite programs. Notably, the combination of a DTV (or an HDTV)and a digital video recorder or player can be an integral part of a hometheater entertainment system.

[0005] A digital video recorder or player typically contains a MovingPictures Expert Group (MPEG) decoder to decode the digitally encodedmultimedia data that is stored on the discs that the recorder or playerplays. If the digital video recorder or player is connected to aconventional (non-DTV or non-HDTV) television display device, thedigitally encoded signal will be decoded by the digital video recorderor player's MPEG decoder before being displayed on the conventionaltelevision display. Significantly, however, many DTV's contain their ownMPEG decoders, as the MPEG decoder in the majority of digital videorecorders or players cannot handle the stringent requirements fordecoding video signals for such televisions receivers As such, if adigital video recorder or player is connected to a DTV, the video signalread from the disc is remotely decoded by the DTV's decoder. Thisconfiguration can be referred to as a remote decoder arrangement.

[0006] There is, however, an important disadvantage to decodingdigitally encoded signals with a remote DTV decoder. Namely, it is verydifficult to perform trick modes in this type of arrangement. A trickmode can be any playback of a video or audio signal at any speed otherthan normal speed or in other than a forward direction. Oftentimes, atrick mode involves repeating a number of pictures in a video signalsuch as during a slow motion trick mode. However, since the bandwidthbetween the digital video recorder or player and the digital televisiondisplay can be limited, repeating pictures in the signal being fed tothe display may cause the signal to exceed the maximum bit rate limit ofthe transmission channel. The problem is even more acute if the picturesare intra (I) pictures or predictive (P) pictures, since these picturesare generally encoded with more bits. Thus, a need exists for a methodand system for performing a trick mode in a remote decoder arrangementwithout exceeding a maximum bit rate limit and without increasing systemcosts or complexity.

SUMMARY OF THE INVENTION

[0007] The present invention concerns a method of performing a trickmode on a video signal containing a plurality of progressively scannedoriginal pictures. The method includes the steps of: in response to atrick mode command, selectively repeating at least one of the originalpictures to convert the video signal to a trick mode video signal; andselectively inserting at least one dummy bidirectional predictivepicture in the trick mode video signal. The method can also include thesteps of: monitoring the trick mode video signal; and selectivelyinserting at least one dummy bidirectional predictive picture in thetrick mode video signal if the bit rate of the trick mode video signalexceeds a predetermined threshold.

[0008] In one arrangement, each of the plurality of original picturescan contain a display indicator, and the method can further include thestep of selectively modifying the display indicator of at least aportion of the plurality of original pictures to reflect an intendeddisplay order when an original picture is repeated or when a dummybidirectional predictive picture is inserted in the trick mode videosignal. The display indicator can be a temporal reference field. Inaddition, each temporal reference field can have an integer value, andthe step of selectively modifying the temporal reference field of atleast a portion of the plurality of original pictures can include thestep of incrementally increasing by one the integer value of thetemporal reference field each time an original picture is repeated andeach time a dummy bidirectional predictive picture is substituted for atleast one of the repeated original pictures in the video signal.

[0009] In one arrangement, the dummy bidirectional predictive picturecan be predicted from a reference picture. Also, each dummybidirectional predictive picture can be a one-directional predictivepicture. Further, the reference picture can be an intra picture or apredictive picture. In another arrangement, at least a portion of thetrick mode video signal can be decoded by a remote decoder.

[0010] The invention also concerns a method of performing a trick modeon a video signal containing a plurality of progressively scannedoriginal pictures in which each of the plurality of progressivelyscanned original pictures contains a display indicator. This methodincludes the steps of: in response to a trick mode command, selectivelyrepeating at least one of the original pictures to convert the videosignal to a trick mode video signal; and selectively modifying thedisplay indicator of at least a portion of the plurality of originalpictures each time an original picture is repeated. In addition, atleast a portion of the trick mode video signal in this embodiment can bedecoded by a remote decoder.

[0011] The invention also concerns another method of performing a trickmode on a video signal containing a plurality of progressively scannedoriginal pictures including the steps of: receiving a trick modecommand; and selectively inserting at least one dummy bidirectionalpredictive picture in the video signal to form a trick mode videosignal. In one aspect of this method, each of the plurality of originalpictures can contain a display indicator and the method can furtherinclude the step of selectively modifying the display indicator of atleast a portion of the plurality of original pictures to reflect anintended display order each time the selectively inserting step isperformed. Also, the display indicator can be a temporal reference fieldin which each temporal reference field can have an integer value and thestep of selectively modifying the temporal reference field of at least aportion of the plurality of original pictures can include the step ofincrementally increasing by one the integer value each time theselectively inserting step is performed. In addition, each dummybidirectional predictive picture can be a one-directional predictivepicture, and at least a portion of the trick mode video signal can bedecoded by a remote decoder.

[0012] The invention also concerns another method of decoding adigitally encoded signal. This particular method includes the steps of:transmitting the digitally encoded signal to a remotely located decoder;and decoding at least a portion of the digitally encoded signal at theremotely located decoder. In this method, the digitally encoded signalcan contain at least one dummy bidirectional predictive picture andadditional pictures, which can be selected from the group includingintra pictures, predictive pictures or bidirectional predictivepictures.

[0013] The present invention also concerns a system for performing atrick mode on a video signal containing a plurality of progressivelyscanned original pictures. The system includes: a controller for readingdata from a storage medium and generating the video signal containingthe plurality of original pictures; and a video processor in which theprocessor is programmed to: in response to a trick mode command,selectively repeat at least one of the original pictures to convert thevideo signal to a trick mode video signal; and selectively insert atleast one dummy bidirectional predictive picture in the trick mode videosignal. The system also includes suitable software and circuitry toimplement the methods as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a block diagram of a system that can perform a trickmode using dummy bidirectional predictive pictures in accordance withthe inventive arrangements herein.

[0015]FIG. 2 is a flow chart that illustrates an operation of performinga trick mode using dummy bidirectional predictive pictures in accordancewith the inventive arrangements.

[0016]FIG. 3 is a flow chart that illustrates an alternative operationof performing a trick mode using dummy bidirectional predictive picturesin accordance with the inventive arrangements.

DETAILED DESCRIPTION

[0017] A system 100 for implementing the various advanced operatingfeatures in accordance with the inventive arrangements is shown in blockdiagram form in FIG. 1. The invention, however, is not limited to theparticular system illustrated in FIG. 1, as the invention can bepracticed with any other system capable of receiving a digitally encodedsignal and transferring that signal to a display device. In addition,the system 100 is not limited to reading data from or writing data toany particular type of storage medium, as any storage medium capable ofstoring digitally encoded data can be used with the system 100.

[0018] The system 100 can include a controller 110 for reading data fromand writing data to a storage medium 112. The system 100 can also have asearching engine 114, a microprocessor 116 and a display device 118. Thesearching engine 114 can contain suitable software and circuitry forlocating one or more particular types of pictures in a video signalrepresentative stream read from the storage medium 112. Control and datainterfaces can also be provided for permitting the microprocessor 116 tocontrol the operation of the controller 110 and the searching engine114. Suitable software or firmware can be provided in memory for theconventional operations performed by the microprocessor 116. Further,program routines can be provided for the microprocessor 116 inaccordance with the inventive arrangements.

[0019] It should be understood that all or portions of the searchingengine 114 and the microprocessor 116 can be a video processor 120within contemplation of the present invention. Further, all or portionsof the controller 110, the searching engine 114 and the microprocessor116 can be a bitstream source 122 within contemplation of the presentinvention. In one arrangement, the display device 118 can contain itsown decoder (not pictured) for decoding all or a portion of any videosignal read from the storage medium 112 and processed by the bitstreamsource 122. In this particular arrangement, the decoder (not shown) inthe bitstream source 122 typically does not decode the video signal readfrom the storage medium 112. This particular embodiment can be referredto as a remote decoder arrangement. It should be noted, however, thatthe invention is not limited to this arrangement, as the invention canbe practiced in other suitable systems.

[0020] In operation, the controller 110 can read a video signalcontaining a plurality of progressively scanned original pictures fromthe storage medium 112. For convenience, the phrase “progressivelyscanned original pictures” will be shortened to “original pictures”throughout the application. In one arrangement, if the microprocessor116 receives a trick mode command such as a slow motion or freezecommand, then the microprocessor 116 can selectively repeat at least oneof the original pictures to convert the video signal to a trick modevideo signal. Thus, the trick mode video signal can contain the originalpictures as well as duplicates of certain original pictures, or repeatedoriginal pictures.

[0021] In addition, during the trick mode command, the microprocessor116, can signal the searching engine 114 to locate one or more suitableoriginal pictures in the trick mode video signal. Once a suitableoriginal picture is located, the searching engine 114 can signal themicroprocessor 116, and the microprocessor 116 can generate acorresponding dummy bidirectional predictive (B) picture. Themicroprocessor 116 can then selectively insert at least one of thecorresponding dummy B pictures such that the dummy B picture is sent tothe display device 118. In this arrangement, the dummy B pictures cantake the place of one or more of the repeated original pictures suchthat the dummy B picture is transmitted to the display device 118 anddisplayed instead of a repeated original picture. It is understood,however, that in lieu of repeating pictures in addition to insertingdummy B pictures, the microprocessor 116 can merely insert dummy Bpictures into the video signal read from the storage medium 112 to forma trick mode video signal.

[0022] In another aspect of the invention, the microprocessor 116 canmonitor the bit rate of the trick mode video signal. If the bit rate ofthe trick mode video signal exceeds a predetermined threshold, then themicroprocessor 116, in conjunction with the searching engine 114, canperform the selectively inserting step discussed above in which at leastone dummy B picture can be inserted in the trick mode video signal.

[0023] In another arrangement, the microprocessor 116 can modify certainportions of information contained within one or more of the plurality oforiginal pictures contained in the trick mode video signal to reflect anintended display order. This modification step can be performed whetheroriginal pictures are repeated or dummy B pictures are inserted in thevideo signal. The overall operation of the invention will be discussedin greater detail below.

Trick Mode Using Dummy Bidirectional Predictive Pictures

[0024]FIG. 2 illustrates a flowchart 200 that demonstrates one way inwhich a trick mode using dummy B pictures can be performed. In onearrangement, the invention can be practiced in a remote decoderarrangement. For purposes of the invention, a remote decoder arrangementcan be any system in which at least a portion of the pictures in a videosignal can be decoded by a decoder that is external to and not under thecontrol of a bitstream source that is providing the pictures to thedecoder. As an example, the bitstream source can be an optical storagemedium player or recorder, such as a digital video player or recorder,that reads multimedia data from an optical storage medium and transfersthis data over a transmission channel to a digital television device,which contains its own decoder. It is understood, however, that theinvention is not limited to this example or even a remote decoderarrangement, as the invention can be practiced in any other suitablesystem or arrangement.

[0025] At step 210, a video signal containing a plurality ofprogressively scanned original pictures can be read. At step 212, atrick mode command can be received. For purposes of the invention, thetrick mode command can be any command in which one or more of theoriginal pictures are to be repeated including a pause or freeze commandor a slow motion command. As shown at decision block 213, it can bedetermined whether at least one of the original pictures is to berepeated. If so, then at least one of the original pictures can beselectively repeated, as shown at step 214. This selective repetitionconverts the video signal to a trick mode video signal.

[0026] If the original pictures are not to be repeated, then theflowchart 200 can continue at step 216 where one or more dummy Bpictures can be selectively inserted in the video signal to form a trickmode video signal. In one arrangement, the insertion of the dummy Bpictures can form a slow motion trick mode video signal. In addition, iforiginal pictures are repeated in accordance with step 214, then one ormore dummy B pictures can also be selectively inserted into the trickmode video signal containing the repeated original pictures. Thus, thetrick mode video signal can contain repeated original pictures, dummy Bpictures or a combination thereof.

[0027] A dummy B picture is a picture that can be predicted from certainpictures and whose motion vectors and discrete cosine transform (DCT)coefficients are set to zero. As such, a dummy B picture contains verylittle information. A dummy B picture's primary purpose is to duplicateor repeat the picture from which it was predicted using very few bits.Thus, a dummy B picture is suitable for replacing certain originalpictures when those original pictures are to be repeated in the trickmode video signal. In one arrangement, the dummy B pictures can replaceone or more of the repeated original pictures such that the dummy Bpictures can be transmitted to a remote decoder rather than certainrepeated original pictures. This insertion and replacement step may behelpful in keeping a bit rate of the trick mode video signal stream at amanageable level, as such video signals tend to be elevated becausenumerous original pictures, particularly those with a large number ofbits, are likely to be repeated during the trick mode command.

[0028] A picture from which a dummy B picture is predicted is commonlyreferred to as a reference picture, and a number of the originalpictures can be reference pictures. The reference picture can be eitheran I picture or a P picture. Since pictures cannot be predicted from a Bpicture, it is unnecessary to replace the duplicates or repeats of anoriginal picture if the original picture is a B picture. That is, if theoriginal picture is a B picture, the repeated B pictures do not have tobe replaced by dummy B pictures. Repeating B pictures, however, shouldnot cause the bit rate of the trick mode video signal to exceed themaximum limit of the transmission channel, as B pictures typicallycontain relatively small amounts of encoded data.

[0029] The following example illustrates how a dummy B picture can beinserted in a trick mode video signal. If a trick mode command such as aslow motion trick mode command is received, a predetermined number oforiginal pictures in the video signal will be repeatedly sent to adisplay device thereby creating a trick mode video signal. This processof repeating pictures may cause the bit rate of the trick mode videosignal to exceed the maximum bit rate of the transmission channel,especially if the trick mode is a very slow trick mode.

[0030] For example, for a slow motion trick mode of {fraction (1/10)}×(1× is normal playback speed), an I picture can be repeated nine times.Such repetition will substantially increase the bit rate of thetransmission channel, as I pictures contain a relatively large amountsof encoded data. By inserting dummy B pictures in the trick mode videosignal such that the dummy B pictures replace the repeated I pictures,the bit rate of the trick mode video signal can be lowered, as dummy Bpictures contain far less encoded data in comparison to an I picture. Itis understood, however, that the invention is not limited to thisparticular example, as the invention can be practiced with othersuitable trick modes.

[0031] In one arrangement, the dummy B pictures that are inserted in thetrick mode video signal can be one-directional prediction pictures. Aone-directional prediction picture is predicted from merely one picture,whereas a B picture is generally predicted from two separate pictures.Typically, the one-directional dummy B pictures can either be forwardpredicted dummy B pictures or backward predicted dummy B pictures. Ifthe dummy B picture is a forward predicted dummy B picture, then thedummy B picture can be predicted from a reference picture that is before(in display order) the dummy B picture. In contrast, if the dummy Bpicture is a backward predicted dummy B picture, then the dummy Bpicture can be predicted from a reference picture that follows (indisplay order) the dummy B picture. Because they are predicted merelyfrom one picture, one-directional prediction dummy B pictures can besuitable for repeating or duplicating pictures.

[0032] In another embodiment, each of the plurality of original picturescan contain a display indicator. As determined at decision block 218, ifthe display indicators of these pictures are to be selectively modified,then the display indicator of at least a portion of the plurality oforiginal pictures can be selectively modified, as shown at step 220.

[0033] Notably, modifying these display indicators can reflect anintended display order of the plurality of original pictures when anoriginal picture is repeated and when a dummy B picture is inserted inthe trick mode video signal. It is understood, however, that thisprocess can be preformed irrespective of whether dummy B pictures areadded during the trick mode. Thus, the step of modifying a displayindicator can be performed during a conventional trick mode in whichpictures are merely repeated and no dummy B pictures are inserted intothe trick mode video signal. Referring back to the flowchart 200, if thedisplay indicators are not to be modified, then the flowchart 200 cancontinue at step 222.

[0034] In one arrangement, the display indicator can be a temporalreference field. A temporal reference field is typically a ten bit fieldlocated in the picture header of digitally encoded pictures. Somedecoders rely on the temporal reference field to determine when aparticular picture in a video signal will be displayed relative to otherpictures in the video signal. This field normally has an integer value.For example, a group of pictures (GOP) generally contains fifteenpictures. The temporal reference field of the first picture in the GOP,i.e., the picture immediately following the GOP header, can have aninteger value of zero. The temporal reference field of the next pictureto be displayed can have an integer value of one. Thus, the integervalue of the temporal reference field for each subsequent picture to bedisplayed can be increased by one count.

[0035] When an original picture is repeated or if a dummy B picture isinserted in the trick mode video signal, however, the display orderaccording to the temporal reference fields of the original pictures isno longer valid. Accordingly, the integer value of the temporalreference fields of the original pictures that follow the inserted dummyB pictures or repeated original pictures can be modified to indicate aproper display order. For example, if the first picture in a GOP is sentto the display device and three corresponding dummy B pictures are sentas well (this is in accordance with a one-fourth slow motion playback),then the integer value of the temporal reference field of the originalreference picture (assuming that it is the first picture in the GOP tobe displayed) can be kept as zero, the temporal reference field of thefirst dummy B picture can be set to an integer value of one, thetemporal reference field of the second dummy B picture can be set to aninteger value of two and the temporal reference field of the third dummyB picture can be set to an integer value of three. In addition, thetemporal reference field of the next original picture to be displayedcan be modified from its original integer value of one to an integervalue of four.

[0036] This step of incrementally increasing the integer values of thetemporal reference fields can continue until the trick mode is rescindedand the temporal reference field of the last picture in the last GOPaffected by the trick mode is modified. Once the next GOP is reached,the integer value of the temporal reference field of the first displaypicture in the new GOP can be zero. Thus, each time a dummy B picture isinserted into the trick mode video signal and each time an originalpicture is repeated, the integer value of the temporal reference fieldsof each original picture following the inserted dummy B pictures and therepeated original pictures can be incrementally increased by onethroughout the trick mode GOPs to reflect the intended display order.

[0037] The integer value for the temporal reference field can have amaximum value of 1,023. If the integer values for the temporal referencefields of the pictures that make up a GOP (the original pictures plusthe dummy B and/or repeated pictures) reach this value, then thetemporal reference field can merely wrap around and begin again at zero.As an example, if a freeze trick mode is initiated and performed for anextended amount of time, the integer value of the dummy B pictures (orrepeat pictures) will eventually reach 1,023. Once that occurs, theinteger value for the temporal reference field of the next immediatedummy B or repeat picture to be displayed can be set to zero. Of course,it should be noted that the invention is not limited to the use of atemporal reference field, as any other suitable display indicator can bemodified to reflect an intended display order in either of theembodiments discussed above. Also, the wrap around value is by no meanslimited to 1,023, as other suitable values can be used. Referring backto the flowchart 200, once the display indicator has been selectivelymodified, the process can continue at step 222. If the trick mode is tocontinue, then the trick mode can continue at step 216. If not, theprocess can stop at step 224.

[0038] Referring to FIG. 3, a flowchart 300 represents an alternative tothe trick mode discussed with respect to flowchart 200. As shown inflowchart 300, steps 310-314 are substantially similar to steps 210-214of flowchart 200 and, accordingly, warrant no discussion here. The onlydifference is that if no pictures are to be repeated as determined atdecision block 313, then the flowchart 300 can continue at step 324. Atstep 316, during the trick mode command, the bit rate of the trick modevideo signal can be monitored. Monitoring the bit rate may be necessaryduring a trick mode because several pictures in the video signal may berepeated one or more times thereby resulting in an increased bit rate.In certain cases, this increased bit rate may exceed the maximumallowable bit rate for the transmission channel that is carrying thevideo signal. For purposes of the invention, this maximum allowable bitrate for the transmission channel can be referred to as a predeterminedthreshold.

[0039] At decision block 318, it can be determined whether the bit rateof the trick mode video signal has exceeded this predeterminedthreshold. If the bit rate has not reached the predetermined thresholdand the trick mode is to continue, then the flowchart 300 can continueat decision block 326. Referring back to step 318, if the bit rate hasexceeded the predetermined threshold, then dummy B pictures can beinserted in the trick mode video signal, as shown at step 324. Also, thedisplay indicators of at least a portion of the original pictures can bemodified, as shown at steps 326 and 328.

[0040] The procedures shown in steps 324, 326 and 328 are similar to thecorresponding procedures illustrated in the flowchart 200. Thus, theinsertion of dummy B pictures can occur based on the monitoring of thebit rate of the trick mode video signal and can be performed if this bitrate exceeds a predetermined threshold. At step 320, it can bedetermined whether the trick mode is to continue. If yes, then theflowchart 300 can resume at step 313. If not, the process can end atstep 322.

[0041] Although the present invention has been described in conjunctionwith the embodiments disclosed herein, it should be understood that theforegoing description is intended to illustrate and not limit the scopeof the invention as defined by the claims.

What is claimed is:
 1. A method of performing a trick mode on a videosignal containing a plurality of progressively scanned originalpictures, comprising the steps of: in response to a trick mode command,selectively repeating at least one of the original pictures to convertthe video signal to a trick mode video signal; and selectively insertingat least one dummy bidirectional predictive picture in the trick modevideo signal.
 2. The method according to claim 1, further comprising thesteps of: monitoring the trick mode video signal; and wherein the stepof selectively inserting at least one dummy bidirectional predictivepicture in the trick mode video signal is done if the bit rate of thetrick mode video signal exceeds a predetermined threshold.
 3. The methodaccording to claim 1, wherein each of the plurality of original picturescontains a display indicator and the method further comprises the stepof selectively modifying the display indicator of at least a portion ofthe plurality of original pictures to reflect an intended display orderwhen an original picture is repeated or when a dummy bidirectionalpredictive picture is inserted in the trick mode video signal.
 4. Themethod according to claim 3, wherein the display indicator is a temporalreference field.
 5. The method according to claim 4, wherein eachtemporal reference field has an integer value and the step ofselectively modifying the temporal reference field of at least a portionof the plurality of original pictures comprises the step ofincrementally increasing by one the integer value of the temporalreference field each time an original picture is repeated and each timea dummy bidirectional predictive picture is inserted in the trick modevideo signal.
 6. The method according to claim 1, wherein each dummybidirectional predictive picture is predicted from a reference picture.7. The method according to claim 1, wherein each dummy bidirectionalpredictive picture is a one-directional predictive picture.
 8. Themethod according to claim 6, wherein the reference picture is an intrapicture.
 9. The method according to claim 6, wherein the referencepicture is a predictive picture.
 10. The method according to claim 1,wherein at least a portion of the trick mode video signal is decoded bya remote decoder.
 11. In a remote decoder arrangement, a method ofperforming a trick mode on a video signal containing a plurality ofprogressively scanned original pictures, wherein each of the pluralityof progressively scanned original pictures contains a display indicator,comprising the steps of: in response to a trick mode command,selectively repeating at least one of the original pictures to convertthe video signal to a trick mode video signal; monitoring a bit rate ofthe trick mode video signal; selectively inserting at least one dummybidirectional predictive picture in the trick mode video signal if thebit rate exceeds a predetermined threshold; and selectively modifyingthe display indicator of at least a portion of the plurality of originalpictures to reflect an intended display order when an original pictureis repeated or when a dummy bidirectional predictive picture is insertedin the trick mode video signal.
 12. A method of performing a trick modeon a video signal containing a plurality of progressively scannedoriginal pictures, wherein each of the plurality of progressivelyscanned original pictures contains a display indicator, comprising thesteps of: in response to a trick mode command, selectively repeating atleast one of the original pictures to convert the video signal to atrick mode video signal; and selectively modifying the display indicatorof at least a portion of the plurality of original pictures to reflectan intended display order each time an original picture is repeated. 13.The method according to claim 12, wherein at least a portion of thetrick mode video signal is decoded by a remote decoder.
 14. A method ofperforming a trick mode on a video signal containing a plurality ofprogressively scanned original pictures, comprising the steps of:receiving a trick mode command; and selectively inserting at least onedummy bidirectional predictive picture in the video signal to form atrick mode video signal.
 15. The method according to claim 14, whereineach of the plurality of original pictures contains a display indicatorand the method further comprises the step of selectively modifying thedisplay indicator of at least a portion of the plurality of originalpictures to reflect an intended display order each time said selectivelyinserting step is performed.
 16. The method according to claim 15,wherein the display indicator is a temporal reference field.
 17. Themethod according to claim 16, wherein each temporal reference field hasan integer value and the step of selectively modifying the temporalreference field of at least a portion of the plurality of originalpictures comprises the step of incrementally increasing by one theinteger value of the temporal reference field each time said selectivelyinserting step is performed.
 18. The method according to claim 14,wherein each dummy bidirectional predictive picture is a one-directionalpredictive picture.
 19. The method according to claim 14, wherein atleast a portion of the trick mode video signal is decoded by a remotedecoder.
 20. A method of decoding a digitally encoded signal, comprisingthe steps of: transmitting the digitally encoded signal to a remotelylocated decoder; and decoding at least a portion of the digitallyencoded signal at the remotely located decoder, wherein the digitallyencoded signal contains at least dummy bidirectional predictive pictureand additional pictures selected from the group comprising intrapictures, predictive pictures or bidirectional predictive pictures. 21.A system for performing a trick mode on a video signal containing aplurality of progressively scanned original pictures, comprising acontroller for reading data from a storage medium and generating thevideo signal containing the plurality of original pictures; and aprocessor, wherein the processor is programmed to: in response to atrick mode command, selectively repeat at least one of the originalpictures to convert the video signal to a trick mode video signal; andselectively insert at least one dummy bidirectional predictive picturein the trick mode video signal.
 22. The system according to claim 21,wherein the video processor is further programmed to: monitor the trickmode video signal; and selectively insert at least one dummybidirectional predictive picture in the trick mode video signal if thebit rate of the trick mode video signal exceeds a predeterminedthreshold.
 23. The system according to claim 21, wherein each of theplurality of original pictures contains a display indicator and thevideo processor is further programmed to modify selectively the displayindicator of at least a portion of the plurality of original pictures toreflect an intended display order when an original picture is repeatedand when a dummy bidirectional predictive picture is inserted in thetrick mode video signal.
 24. The system according to claim 23, whereinthe display indicator is a temporal reference field.
 25. The systemaccording to claim 24, wherein each temporal reference field has aninteger value and the step of selectively modifying the temporalreference field of at least a portion of the plurality of originalpictures comprises the step of incrementally increasing by one theinteger value of the temporal reference field each time an originalpicture is repeated or when a dummy bidirectional predictive picture isinserted in the trick mode video signal.
 26. The system according toclaim 21, wherein each dummy bidirectional predictive picture ispredicted from a reference picture.
 27. The system according to claim21, wherein each dummy bidirectional predictive picture is aone-directional predictive picture.
 28. The system according to claim26, wherein the reference picture is an intra picture.
 29. The systemaccording to claim 26, wherein the reference picture is a predictivepicture.
 30. The system according to claim 21, further comprising aremote decoder for remotely decoding at least a portion of the trickmode video signal.
 31. A remote decoder system for performing a trickmode on a video signal containing a plurality of progressively scannedoriginal pictures, wherein each of the plurality of progressivelyscanned original pictures contains a display indicator, comprising: acontroller for reading data from a storage medium and generating thevideo signal containing the plurality of original pictures; and aprocessor, wherein the processor is programmed to: in response to atrick mode command, selectively repeat at least one of the originalpictures to convert the video signal to a trick mode video signal;monitor a bit rate of the trick mode video signal; selectively insert atleast one dummy bidirectional predictive picture in the trick mode videosignal if the bit rate exceeds a predetermined threshold; andselectively modify the display indicator of at least a portion of theplurality of original pictures to reflect an intended display order whenan original picture is repeated or when a dummy bidirectional predictivepicture is inserted in the trick mode video signal.
 32. A system forperforming a trick mode on a video signal containing a plurality ofprogressively scanned original pictures, wherein each of the pluralityof progressively scanned original pictures contains a display indicator,comprising: a controller for reading data from a storage medium andgenerating the video signal containing the plurality of originalpictures; and a processor, wherein the processor is programmed to: inresponse to a trick mode command, selectively repeat at least one of theoriginal pictures to convert the video signal to a trick mode videosignal; and selectively modify the display indicator of at least aportion of the plurality of original pictures each time an originalpicture is repeated.
 33. The system according to claim 32, furthercomprising a remote decoder, wherein the remote decoder decodes at leasta portion of the trick mode video signal.
 34. A system for performing atrick mode on a video signal containing a plurality of progressivelyscanned original pictures, comprising: a controller for reading datafrom a storage medium and generating the video signal containing theplurality of original pictures; and a video processor programmed to:receive a trick mode command; and selectively insert at least one dummybidirectional predictive picture in the video signal to form a trickmode video signal.
 35. The system according to claim 34, wherein each ofthe plurality of original pictures contains a display indicator and theprocessor is further programmed to selectively modify the displayindicator of at least a portion of the plurality of original pictures toreflect an intended display order each time the processor performs theselectively inserting step.
 36. The system according to claim 35,wherein the display indicator is a temporal reference field.
 37. Thesystem according to claim 35, wherein each temporal reference field hasan integer value and the processor is further programmed to selectivelymodify the temporal reference field of at least a portion of theplurality of original pictures by incrementally increasing by one theinteger value of the temporal reference field each time the processorperforms the selectively inserting step.
 38. The system according toclaim 34, wherein each dummy bidirectional predictive picture is aone-directional predictive picture.
 39. The system according to claim34, further comprising a remote decoder, wherein the remote decoderdecodes at least a portion of the trick mode video signal.
 40. A systemfor decoding a digitally encoded signal, comprising: a remotely locateddecoder; and a transmission channel for transmitting the digitallyencoded signal to the remotely located decoder, wherein the remotelylocated decoder decodes at least a portion of the digitally encodedsignal, wherein the digitally encoded signal contains at least one dummybidirectional predictive picture and additional pictures selected fromthe group comprising intra pictures, predictive pictures orbidirectional predictive pictures.